Apparatus for detecting holes in fabric



y 1956 R. c. BAKER 2,748,381

APPARATUS FOR DETECTING HOLES IN FABRIC Filed Oct. 14, 1952 2Sheets-Sheet l /01/ 60m Ac INVENTOR For GEE/ 13 HIS ATTORNEYS May 29,1956 R. C. BAKER APPARATUS FOR DETECTING HOLES IN FABRIC Filed 001.. l4,1952 2 Sheets-Sheet 2 1 N VENTOR H/S ATTORNEYS APPARATUS FOR DETEC'HNGHQLES IN FABRIC Roy C. Baker, Winston-Salem, N. (1.

Application October 14,1952, Serial No. 314,586

19 Claims. (62. 34t)259) This invention relates to an apparatus fordetecting holes in fabric, and more particularly tubular knitted fabric.

Various types of apparatus have been developed for detecting holes intubular knitted fabric. These machines for the most part employ feelerfingers movable through a hole in the fabric to contact with some metalportion of the knitting machine to complete an electrical circuit tosound an alarm, illuminate a warning light, stop the apparatus, orotherwise perform some function to indicate that a defect has beenfound. paratus are easily adaptable for use for detecting holes intubular knitted fabric as it leaves the knitting machine, since one sideof the detecting or warning circuit can be grounded on the knittingmachine, thus rendering it comparatively simple to complete a circuitthrough the feeler fingers when a hole passes one of these fingers.

On the other hand, such an apparatus is not adaptable for use where thefabric moves relatively rapidly past the feeler fingers, since theperiod during which electrical contact is established by the fingersdoes not provide the in terval of time necessary for causing theoperation of the warning devices, etc. in mechanical devices associatedwith the detecting circuits, the inertia of the moving parts does notpermit them to become operative. Moreover, apparatus of the characterreferred to can be used only on tubular knitted fabric as it leaves theknitting machine, and it is highly desirable to provide hole detectingmeansv for fabric of this kind, which will be operative at relativelyhigh speeds of movement of the fabric and will be operative on fabricmoving from machines or equipment not associated with the knittingmachine, for example after such operations as bleaching, centrifuging,and drying, and in some instances also after dyeing the material.

An important object of the present invention is to provide a novel holedetecting mechanism particularly adapted for use in detecting holes intubular knitted fabric after it has left a knitting machine, and whereinsuch apparatus is operative for performing the desiredfunctionsof'operating a warning signal, etc., even though the materialis moving at a relatively high speed.

A further object is to provide such an apparatus which possesses suchcharacteristics that even though the fabric is moving at a relativelyhigh speed and the normal period of electrical contact of the feelerfingers is extremely short, the problem of overcoming the inertia ofmovable parts, etc. is not present.

A further object is to provide an apparatus of this character havingnovel means for completing a circuit through any feeler finger when thelatter encounters a hole in the fabric.

A further object is to provide a novel apparatus which is operativemechanically by any feeler finger for establishing a holding cicuit forthe proper operation of warning signals, etc.

A further object is to provide a novel type of what may be termed afloating spreader formed of electri- Such forms of ap-- a: calconducting material and arranged in the tubular goods passing thereover,and to provide novel means for connecting the spreader in a circuit soas to render it ready for operation at all times for completing adetecting circuit through any feeler finger which may encounter a holein the knitted fabric.

A further object is to provide in an apparatus of this character arotating member mounted within the spreader and having needle-likecontact elements which project through the fabric to maintain constantelectrical engagement with a rotary member outside the fabric so as tocomplete a circuit at all times for the detecting mechanism, except atthe feeler fingers, whereby contact of any such fingers with thespreader operates the detecting mechanism.

Av further object is to provide a novel type of spreader whereinthe-fabric is caused to partake of an abrupt bend at each side of thespreader at the points where the feeler' fingers contact with thefabric, thus rendering the fingers operativefo-r detecting relativelysmall holes in the fabric.

A further object is to provide an apparatus of this generalcharacterwherein mechanical movement imparted to any feeler finger is translatedinto operation of a switch to energize a signal or similar holdingcircuit and wherein the mechanical operation is accomplished withoutundue resistance against movement of an operative feeler finger, thuspreventing the latter from substantially enlarging the hole which is inengagement with such finger.

A further object is to provide, in combination with an apparatus of thischaracter, a highly efiicient electronic control circuit which permitsthe use of a low voltage detecting circuit to prevent arcing at any ofthe contact points in suclrcircuit, and which is operable even if thefeeler' contact is established for a very small fraction of a second,toinsure the operation of the alarm or warning circuit.

Other objects and advantages of the invention will become apparent inthe course of the following description.

In the drawings 1 have shown two embodiments of the invention. In thisshowing:

Figure 1 is a diagrammatic representation of the apparatus and itsdetecting and alarm or control circuits;

Figure. 2 is a fragmentary sectional view through the spreader and thefabric feed rolls which maintain the spreader in position, a portion ofthe fabric being shown passing through the apparatus and feeler fingersbeing illustrated at opposite sides of the spreader;

Figure 3 is a fragmentary end elevation of what may be termedthe. needlewheel and a portion of its cooperating contact wheel, a layer of fabricpassing between these wheels being shown in. dotted lines;

Figure 4 is a fragmentary sectional view on line 4-4 of Figure 2;

Figure 5 is a similar view on line 5-5 of Figure 2;

Figure 6 is a sectional view similar to Figure 2' showing a modifiedform of the invention; and

Figure 7 is a plan view of the switch operating means employed in theform of the invention shown in Figure 6.

Referring to Figures 2, 4, and 5, the. numeral 10 designates a spreadershown in the present instance as being a relatively thin metallic platearranged vertically, and of such horizontal width as to facilitate itsentering a tubular fabric 11 of a particular size. The spreadershorizontal cross section area will be such as to slightly stretch thetubular fabric so that the latter will be maintained smooth and flat onopposite sides of the spreader. edges of the spreader are preferablyrounded, as indicated by the numeral 12. Such edge at the top of thespreader facilitates smooth entrance of the top of the spreader into thefabric as the latter moves downwardly thereover, and

g the rounding of the side edges of the spreader facilitates the smoothsliding movement of the fabric thereover, as will be apparent.

Beneath the spreader are a pair of feed rolls 13 mounted on shafts 14 tobe driven thereby in any suitable manner, these rollers rotating in thedirection of the arrows in Figure 2. These rollers may be covered ontheir surfaces with any layer of material 15 which will possess asufiicient degree of surface friction to facilitate the feeding of thetubular fabric downwardly between the rollers. The space between therollers is only sufficient for the passage of the fabric therebetween,and this space is much narrower than the thickness of the spreader 10.Therefore, while the adjacent sides of the rollers move downwardly tofeed the fabric therebetween, the rollers act as supporting means forthe spreader 12.

The spreader is provided at opposite sides with undercut shoulders 16beneath which the spreader is relatively thin and tapers to increase inwidth as at 17, the spreader above the shoulders 16 and beneath thetapered portion 17 having each of its opposite faces lying in a commonplane. It will be apparent that the fabric passing over the shoulders 16partakes of an abrupt bend, and it is at this point that feeler fingersengage the fabric to slide thereover unless and until a hole in thefabric, for example as indicated by the numeral 18, passes over one ofthe fingers to operate the detecting circuit.

Each of the feeler fingers is indicated as a whole by the numberal 2h. Aset of these fingers is arranged outwardly of each side of the spreaderand the fingers of each set are arranged in close proximity, for exampleone-eighth inch apart in actual practice, so as to render itsubstantially impossible for a hole to pass between any adjacent pair offingers. All of the fingers will be identical and only one need bedescribed in detail. Each finger is made of spring wire of circularsection, and the end remote from the spreader is coiled as at 21 and hasits extremity projecting through a supporting bar 22. From the coil 21each finger extends downwardly and inwardly toward the spreader 10, asat 23, and then curves upwardly, as at 24, toward the adjacent shoulder16. Just beneath such shoulder, the spreader is looped as at 25 and hasits extremity 26 extending downwardly and away from the spreader. Theloop 25 of each feeler finger provides a smooth surface under which thefabric is adapted to slide, but when a hole 18 passes one of the loops25, this loop will extend through the hole and engage the spreader toclose a detecting circuit in a manner to be described. The tensioning ofeach finger 23 is such that the tendency for each loop 25 is to moveupwardly and inwardly toward the shoulders 16, substantially asindicated by the small arrows in Figure 2. This tensioning of thefingers greatly facilitates the entrance of any loop 25 through a hole18 as the latter takes its abrupt bend in passing around one of theshoulders 16.

As previously stated, it is a simple matter in a hole detecting deviceassociated with a knitting machine to ground the detecting circuit onsuch machine. The present apparatus may be used anywhere it may bedesired, wholly disassociated from a knitting machine, and it will beapparent that the spreader 10 is housed wholly within the tubularfabric, thus rendering it difiicult to connect the spreader into adetecting circuit. The present apparatus, in the form shown in Figures1-5 inclusive, provides a novel means for electrically connecting thespreader 10 in a detecting circuit so that such circuit is normallybroken solely at the feeler fingers. Referring to Figures 3 and 5, thenumeral 30 designates a wheel mounted in a recess 31 formed in thespreader plate, assuming this plate to be a solid member, asspecifically illustrated. The roller 30 is mounted on a shaft 32extending through the walls of the spreader 10 at opposite sides of therecess 30, but obviously not projecting beyond the outer surfaces of thespreader since this would interfere with the movement of the fabricthereover. The wheel 31) is metal, as is its shaft 32 and, accordingly,the wheel is grounded on the metallic spreader 10. Around its periphery,the wheel 30 is provided with closely arranged needles 33. Theseelements are contact elements made of resilient material of smalldiameter and are actually needle-like in that they are pointed for thefree penetration thereof through the fabric 11. In actual tests it hasbeen found that the needles 33 may be radially arranged without damageto the fabric, but possible damage is completely eliminated by incliningthe needles away from the direction of rotation of the wheel 36, asindicated in Figure 3.

The needles 33 are longer than the thickness of the fabric passing overthe wheel 30, as shown in Figures 3 and 5, and the needles engage acontact wheel 34 suitably supported on a shaft 35 parallel to the shaft32. The wheel 34 of course is made of electrically conducting material,and preferably of a commercially available rubber material havingoccluded conducting substances therein which are concentrated to providethe necessary conductivity. Alternatively, the wheel 34 may be a steelbristle brush with the steel bristles closely arranged, or it may bemade up of steel or copper wool clamped between round plates. Variousother types of wheels may be employed including soft lead or otheralloy. In other words, as a practical matter, the wheel 34 should bemade of such material as to establish good electrical contact with theneedles 33 without rapidly wearing the ends of such needles. Theseneedles, in any event, preferably possess a substantial degree ofresiliency, and the length of the needles, the spacing of the needles,and the diameter of the wheels 30 and 34 are such that the wheel 34 isnever without firm contact with at least one needle and preferably two,as shown in Figure 3. Therefore, whenever the circuit otherwise isclosed, there can be a continuous flow of current between wheels 30 and34 without any making or breaking of the circuit between these wheels,and arcing is effectively prevented.

In Figure 1, highly eificient electrical control circuits for theapparatus are illustrated. A source of current, such as a battery 36, ofthe order of 45 volts, has the positive terminal thereof connected by awire 37 to the bars 22, which are formed of conducting material, andconnected in parallel, as shown in Figure l. The spreader 10 has beenmerely diagrammatically indicated in Figure 1 without reference to themounting of the wheel 30 thereon, and this wheel has been shown for thepurpose of illustration as being electrically connected to the spreader,as at 38. It will be apparent that the wheel 30 is parallel to theopposite faces of the spreader 10 and, accordingly, normally occupies aposition perpendicular to its position as diagrammatically shown inFigure l.

The negative terminal of the battery 36 is connected to a wire 39 whichconnects to the grid 42b of electron tube 42. Electron tube 42 includes,in addition to control grid 42b, cathode .2a, and anode or plateelectrode 420. The input circuit to the tube 42 is completed throughlead 40 which connects to the wheel 34 with a suitable condenser 41connected between grid 42b and cathode 42a. The electrical elementsdescribed constitute the detecting circuit portion of the apparatus, andwhat may be termed the control circuit is controlled from the detectingcircuit.

The circuit components of the detecting circuit are all selected so thattube 42 operates on very high contact resistance which is highlynecessary for the successful functioning of the hole detector. I havesuccessfully used a 615 tube as the tube 42 and have so designed thecircuit that contact between the finger 24B and the spreader 10 may beextremely light and rapid and yet sufficient to impress a voltage ofminute magnitude on the control grid 42b resulting in a current flow ofthe order of microamperes to effect the required control without contactarcing. Arcing within the textile fabric is dangerous due to liabilityof injury and the hazard of fire. The microampere current necessary toperform a control function is so low that contact arcing is invisibleand cannot be- Z3 come a source of hazard. A contact interval as rapidas .003 second is sufiicient to effect a functioning of the relay shownat 43 in the output circuit of the control system which makes itpossible to operate the inspection device at approximately sixty feetper minute without taking into consideration the wiping effect of theprobe fingers which can double or treble the speed of operation of thesystem of my invention.

The output circuit of tube 42 includes an appropriate source of platepotential 44 of the order of 45 volts and there is a suitable source ofpotential 45 for supplying the cathode heating current with a suitableswitch 46 for turning on the electronic circuit by closing the cathodeheating circuit when the device is to be placed in operation. The relay43 is a high-resistance, highly-sensitive single pole, double throwdevice including armature 43a spring biased by spring 43b to a positionnormally in contact with contact 47 for preparing the circuit throughalarm horn 51 and through a switch 53 to the power supply circuit 49.Switch 53 is not closed until tube 42 is brought up to full operatingcondition. The relay armature 43a is movable when relay 43 is energizedto open contact 47 and close contact 50, connecting lamp 48 to thealternating current power supply circuit 49. The condenser 41 whichshunts the cathode 42a and control grid 42b is arranged in the inputcircuit.

When the electronic circuit is conditioned for operation by closingswitch 46 to heat the cathode, current fiows in the output circuit andwith the control grid 42b substantially floating by reason of the factthat the circuit through fingers 2t and spreader is opened, relaywinding 43 is energized as soon as the tube 42 is raised to operatingtemperature, moving armature 43a to contact 50 and energizing signallamp 48, thus showing that the electronic circuit of tube 42 is inproper operating condition. The circuit to the horn 51 is normallymaintained open while the circuit of tube 42 is being conditioned foroperation.

Thus the cathode 42a preferably is conditioned for the requiredelectronic emission before the circuit for the horn 51 is conditioned torespond to operation of the detecting circuit. For accomplishing thisend, the switch 46 is first closed, and after a suitable time interval,switch 53 in the circuit of the horn 51 is closed. By the time theswitch 53 has been closed, plate current will be passing through winding43 so that the circuit through contact 47 and armature 43a will be open,and the horn 51 will be silent. However, when a contact occurs betweenfingers 20 and spreader lift, the plate current is immediately blockedand winding 43 is de-energized, whereby armature 43a is released andmoves under tension of spring 43b to establish connection with contact47, thus completing the circuit through closed switch 53, horn 51 andpower source 49, sounding the alarm denoting a fault in the cloth. Thecapacity of condenser 41 predetermines the time period of operation ofthe circuits. Condenser 41 in the input circuit is charged when thenegative potential from battery 36 is applied to control grid 42b andcontinues to hold its charge after the momentary contacts betweenfingers 2% and spreader 10 of the hole detector are opened. As soon asthe grid 42b of tube 42 becomes negative, as hereinbefore pointed out,current flow to the anode is stopped, winding 43 de-energized and relaycontact 47 closed by armature 43a being released under tension of spring43b, thus closing the circuit through horn 51. The condenser 41 isrelatively large and maintains the grid voltage at a sufficient levellong enough for relay 43 to remain dc-energized and the alarm circuitclosed.

When the opening in the fabric has passed by the fingers 20 and thespreader 1d, the negative potential from battery 36 is removed from grid42b and current again flows in the output circuit of tube 42 excitingwinding 43 and moving armature 43a into connection with contact 50,closing the circuit between armature 43a and contact 50' and lightingsignal lamp 48 from the power source 49.

The circuit to the alarm or horn 51 is broken between contact 47 andarmature 43a subject to be made as soon as fingers 22 again encounter anopening in the fabric passing over spreader 10.

In lieu of the battery powered circuit that I have diagrammaticallyshown, I may power the circuit with rectified and filtered alternaitngcurrent. When this latter type of power is used, a condenser of theorder of 1 m. f. d. at 200 volts is connected in shunt with the windingof relay 43 for maintaining the voltage across the relay winding duringthe half cycle when the tube 42 allows current to pass in one directiononly.

it will be apparent that with the form of the invention described aboveand as further referred to below, an extremely short interval of contactbetween one of the fingers 2i? and the spreader it is sufficient for theoperation of the alarm circuit. In Figures 6 and 7 I have shown amodified form of the invention in which the same type of spreader andfeed rolls 13 and 14 have been employed, and these elements have beenindicated by the same numerals in Figure 6, together with other elementswhich are common to the two forms of the invention. In the modified formthe spreader 10 is not depended upon as an electrical conductor, and thefeeler fingers function mechanically to close an alarm circuit in anovel manner. The feeler fingers are identical with those describedabove, except that instead of the terminating end 26, the fingersbeneath and outwardly of the loops 25 extend downwardly as at 65 to forma mechanical contact loop 66, and then upwardly as at 67 to be braced orwelded to the finger portions 23.

Outwardly of each side of the spreader is arranged a switch operatingwheel 70 fixed toa shaft 71 to be rocked thereby. Beyond the ends of thefeelers, sleeves 72 are fixed to each shaft 71, and a substantiallyU-shaped frame 73 is provided at its ends with arms 74 fixed to thesleeves 72. Each frame 73 further includes a mechanical contact bar 75connected between the arms 74, this bar being parallel to the shaft 71and parallel to the adjacent side face of the spreader 10.

Each wheel 70 is provided in its periphery with a curved notch '76 toreceive a cam offset 77 formed on a switch operating finger 78,supported as at 79. The free end of each finger 78 engages a rod 80capped by an insulating element 31. The cap 81 engages a switch finger82 the contact of which is spaced from a second switch finger 83. Asource of current, for example, a battery 34, has one terminal connectedby a Wire 85 to the switch arm 83 and has its other terminal connectedas at 86 to the switch arm 82 with an alarm or indicator 87 connected insuch wire, for example, an electrically operated horn or the like.

Operation As previously stated, the present invention is particularlyintended to provide means for detecting holes in tubular knitted fabricafter the fabric leaves the knitting machine. For example, the fabricsubsequent to knitting may have been subjected to bleaching,centrifuging, and drying; and, in some instances, may have been dyedprior to being subjected to the action of the present apparatus. Fromwhatever operation the tubular fabric is brought to the machine, it isslipped over the spreader l2 and its advancing end is engaged betweenthe rollers 13 to be fed downwardly thereby as viewed in Figure 1. Inthe absence of any holes therein, the fabric will move between the loops25 of the feeler fingers and the spreader, and no operation will takeplace. At all times, however, the movement of the fabric (Figure 3) overthe needles 33 rotates the wheel 30, the needles penetrating the fabricand establishing constant electrical connection between wheels 3% and34. Both of these wheels are freely rotatable, and the fine pointedneedles extend through the fabric and move therewith between the wheels30 and 34 without causing any damage to the fabric.

ejaa abi Assuming that a hole 18 comes into position with respect to oneof the finger loops 25, the fabric adjacent the hole will partake of anabrupt bend around the shoulder 16, thus tending to open the hole andrender it easier for the loop to move therethrough into electricalcontact with the spreader it). When this occurs, a detecting circuitwill be completed from the battery 36 through whichever feeler finger isin electrical engagement with the spreader 1t and across wheels and 34.The closing of this circuit is used to render operative the electronicalarm or control circuit as described above.

In the form of the invention shown in Figures 1-5 inclusive, andassuming that the tubular fabric is passing through the device at aspeed of 60 feet per minute, the duration of the contact of one of thefinger loops 25 will depend upon the size of the hole in the fabric. Inthe case of a one-eighth inch hole the duration of the contact will beonly 0.10 second. As previously stated, this interval of the closing ofthe detecting circuit is not sufficient for the operation of anypreviously known mechanical device in an alarm circuit, and thisdeficiency is overcome by the novel electronic means described herein.In Figures 6 and 7, there is provided a form of the device which isrendered highly efficient in operation because of the use of theshoulder detector for mechanically establishing and maintaining an alarmor control circuit without utilizing the spreader 10 as an electricalconductor. Assuming that a hole 18 in the fabric passes over one of theshoulders 16 and engages one of the small feeler loops 25, the abruptbending of the material around the shoulder insures the entrance of thefeeler finger loop therethrough, and consequently insures mechanicalengagement of the upper edge of the hole in the fabric with the loop 25.This mechanical engagement of the hole with the feeler fingers is farmore positive with the type of spreader illustrated than would be truewith a flat-sided spreader.

The loading of the spring loops 21 of the feeler fingers is notsubstantial but is sufficient to tend to maintain the loop 25 of eachfinger in engagement with the hole in the goods, and without exertingany very great mechanical force against the loop 25, force will betransmitted through the finger portion 65 to the loop 66 to pressdownwardly on the bar '75. In practice, the leverage represented betweenthe length of each arm 74 and the radius of each wheel 70 wil be suchthat little force will be required to rock the Wheel 70 associated withthe feeler finger being operated to turn such wheel and lift the camelement 72 out of the associated notch 76. The arm 78 will be biaseddownwardly by its own resilience or by a light spring, when the camportion 77 is in the notch 76, to support the weight of the frame 73,thus making it possible to rock the wheel 70 with very little force andthus avoiding enlarging the hole in the fabric.

Upon the lifting of the finger 78, the rod 80 and its insulating cap 31will be moved upwardly to engage switch arm 82 with the arm 83 and thusclose a circuit through the alarm 37. The frame 73 may drop to a lowervertical position but will move no further and, accordingly, thecircular portion of the wheel 79 will maintain the switch S2 closed, andthis circuit will remain closed until the operated frame 73 is manuallyrestored to its normal position as shown in Figure 6.

I claim:

1. Apparatus for detecting holes in tubular fabric, comprising aspreader of conducting material around and over which the fabric passesin one direction lengthwise of the fabric, a feeler engageable with thefabric outwardly of said spreader and movable into electrical contacttherewith upon the passing of a hole in the fabric under said feeler,and a detecting circuit including said feeler and said spreader, saidcircuit further comprising a pair of contact devices, one carried by andelectrically connected to said spreader, and the other arrangedexternally of the fabric and in electrical engagement with said onecontact device throughout movement of the fabric over said spreader.

2. Apparatus for detecting holes in tubular fabric, comprising aspreader of conducting material around and over which the fabric passesin one direction lengthwise of the fabric, a feeler engageable with thefabric outwardly of said spreader and movable into electrical contacttherewith upon the passing of a hole in the fabric under said feeler,and a detecting circuit including said feeler and said spreader, saidcircuit further comprising a pair of contact devices, one of which isrotary and is carried by and electrically connected to said spreader,and the other of which is arranged externally of the fabric, said rotarycontact device having circumferentially spaced needle-like fingersprojecting from the periphery thereof to be engaged by the fabric torotate said rotary contact device as the fabric passes thereover, atleast one of said needle-like fingers projecting through the fabric andelectrically contacting the other of said contact devices at all timesduring movement of the fabric over said spreader.

3. Apparatus for detecting holes in tubular fabric, comprising aspreader of conducting material around and over which the fabric passesin one direction lengthwise of the fabric, a feeler engageable with thefabric outwardly of said spreader and movable into electrical contacttherewith upon the passing of a hole in the fabric under said feeler,and a detecting circuit including said feeler and said spreader, saidcircuit further comprising a pair of rotatable contact devices, one ofwhich is mounted in and rotatably supported by said spreader and inelectrical contact therewith and is provided on its periphery with aplurality of relatively closely arranged needle-like fingers each of alength greater than the thickness of the fabric and projectingtherethrough adjacent the other of said contact devices, said othercontact device being formed of relatively deformable conducting materialand being engaged by at least one of said needle-like fingers, to berotated thereby and to compiete the circuit between said contact devicesat all times during movement of the fabric over said spreader.

4. Apparatus for detecting holes in tubular fabric comprising a spreaderaround and over which the fabric passes, common means for feeding thefabric in one direction over said spreader and for preventing movementof said spreader in said direction, a feeler supported outwardly of saidspreader and having a free resilient end engageable against the fabricpassing thereover to be movable through a hole in the fabric, anddetecting means responsive to such movement of said feeler end throughthe fabric.

5. Apparatus for detecting holes in tubular fabric comprising a spreaderaround and over which the tubular fabric passes, a pair of feed rolls atone end of said spreader and between which the fabric is gripped to moveit in one direction over said spreader, the space between said rollsbeing less than the thickness of said spreader to prevent movementthereof in said direction, a feeler supported externally of saidspreader and having an end biased into engagement with the fabricpassing over said spreader to move through a hole in the fabric if suchhole passes beneath said end of said feeler, and means comprising anelectric circuit connected to be closed by said feeler upon movement ofsaid end of said feeler through a hole in the fabric.

6. Apparatus for detecting holes in tubular fabric comprising a spreaderaround and over which the tubular fabric passes, a pair of feed rolls atone end of said spreader and between which the fabric is gripped to moveit in one direction over said spreader, the space between said rollsbeing less than the thickness of said spreader to prevent movementthereof in said direction, a feeler supported externally of saidspreader and having an end biased into engagement with the fabricpassing over said spreader to move through a hole in the fabric if suchhole passes beneath said end of said feeler, a control circuit andswitch means for said circuit having mechanical connection with saidfeeler to be closed by the latter upon movement thereof through a holein the fabric.

7. Apparatus for detecting holes in tubular fabric comprising arelatively thin spreader having opposite faces and insertable in tubularknitted fabric, means for feeding the fabric in one direction over saidspreader, said opposite faces having shoulders undercut in saiddirection, a plurality of feelers supported outwardly of each face ofsaid spreader and having free ends resiliently engageable with thefabric to move through an opening passing beneath any such feeler, thefree end of each of said feelers being arranged beneath one of saidshoulders, whereby the fabric partakes of a relatively sharp bend aroundeach shoulder to facilitate the entrance of any feeler end through afabric hole passing thereover, and means responsive to movement of anyfeeler through a hole in the fabric for closing a control circuit.

8. Apparatus constructed in accordance with claim 7 where in saidspreader and said feelers are formed. of conducting material, and adetecting circuit including said feelers and said spreader, the meansfor closing said control circuit comprising electrical means responsiveto the closing of said detecting circuit.

9. Apparatus constructed in accordance with claim 7 wherein the meansfor closing said control circuit comprises a switch in such circuit, anoperating member for said switch biased therewith to an open-switchposition, and mechanical means responsive to movement of any of saidfeelers through the fabric for moving said switch operating member toclose said switch.

10. Apparatus constructed in accordance with claim 7 wherein the meansfor closing said control circuit comprises a switch in such circuit, anoperating member for said switch biased therewith to an open-switchposition, a notched wheel, an arm having an element normally arranged inthe notch of said wheel and arranged beneath said switch operatingmember to support the latter, and mechanical means having connectionwith said feelers to be operated thereby to turn said wheel to move saidarm and lift said switch operating member to close said switch.

11. Apparatus for detecting holes in tubular fabric, comprising aspreader having opposite faces and insertable into the tubular fabric,feed rolls at one end of said spreader engageable with the fabric tomove it in one direction over said spreader, the space between saidrolls being less than the thickness of said spreader whereby the latteris prevented from moving in said direction, each of said opposite faceshaving a shoulder undercut in said direction, a plurality of feelerfingers arranged outwardly of said opposite faces and each having a freeend resiliently engaging against the fabric just beneath one of saidshoulders whereby the fabric is caused to partake of an abrupt bend oversaid shoulders in passing beneath said ends of said fingers tofacilitate the entrance of said feeler finger ends through holes in thefabric, and electrical control means responsive to movement of any ofsaid feeler fingers through an opening in the fabric.

12.. Apparatus for detecting holes in tubular fabric, comprising aspreader having opposite faces and insertable into the tubular fabric,feed rolls at one end of said spreader engageable with the fabric tomove it in one direction over said spreader, the space between saidrolls being less than the thickness of said spreader whereby the latteris prevented from moving in said direction, each of said opposite faceshaving a shoulder undercut in said direction, a plurality of feelerfingers arranged outwardly of said opposite faces and each having a freeend resiliently engaging against the fabric just beneath one of saidshoulders whereby the fabric is caused to partake of an abrupt bend oversaid shoulders in passing beneath said ends of said fingers tofacilitate the entrance of said feeler finger ends through holes in thefabric,

said feeler fingers and said spreader being formed of conductingmaterial, and a detecting circuit including said feeler fingers and saidspreader, said detecting circuit further including means carried by saidspreader and operable through the fabric for completing said circuitwhenever one of said fingers moves through a hole in the fabric intoelectrical contact with said spreader.

13. Apparatus for detecting holes in tubular fabric, comprising aspreader having opposite faces and insertable into the tubular fabric,feed rolls at one end of said spreader engageable with the fabric tomove it in one direction over said spreader, the space between saidrolls being less than the thickness of said spreader whereby the latteris prevented from moving in said direction, each of said opposite faceshaving a shoulder undercut in said direction, a plurality of feelerfingers arranged outwarly of said opposite faces and each having a freeend resiliently engaging against the fabric just beneath one of saidshoulders whereby the fabric is caused to partake of an abrupt bend oversaidv shoulders in passing beneath said ends of said fingers tofacilitate the entrance of said feeler finger ends through holes in thefabric, said feeler fingers and said spreader being formed of conductingmaterial, and. a detecting circuit including said feeler fingers andsaid spreader, said detecting circuit further comprising a wheel carriedby said spreader within the fabric and provided with peripheralneedle-like fingers projecting through the fabric, said wheel beingfreely rotatable by movement of the fabric over said needlelike fingersas the latter project through the fabric, and rotatable means externallyof the fabric in constant electrical engagement with at least one ofsaid needle-like fingers, whereby said circuit will be completedwhenever one of said feeler fingers moves through an opening in thefabric into electrical contact with said spreader.

14. In apparatus for detecting holes in tubular fabric, means forfeeding the fabric in spread condition, an electric detecting circuitincluding an electron tube having input and output circuits, acircuit-closing element projectable through a hole in the fabric whenthe hole passes a predetermined position during the feeding of thefabric for establishing a conductive connection through the hole in thefabric for closing an electric circuit through the input circuit of saidelectron tube, a potential source in said circuit, means connected withsaid input circuit comprising a condenser having a capacity sufficientto receive a charge from said potential source while said circuitclosing element is closed for a time interval as small as 0.10 secondsand to maintain said change for prolonging the effect of saidcircuit-closing operation beyond the time interval that said circuitclosing element remains closed, and an alarm operative over the timeperiod that said effect of said circuit-closing operation is prolongedpowered from the discharge of said condenser.

15. In apparatus for detecting holes in tubular fabric, means forfeeding the fabric in spread condition, an electric detecting circuitincluding a circuit-closing element projectable through a hole in thefabric when the hole passes a predetermined position during the feedingof the fabric for closing an electric circuit, a potential source anelectron tube including at least a cathode, a control grid and an anode,an input circuit connected with said control grid and cathode, an outputcircuit connected with said anode and cathode, a relay in said outputcircuit, a visual signal, an audible signal, a two-position armaturecontrolled by said relay, contactors operated by said armature andrespectively connected with said signals and a power source forseparately energizing said signals, means for energizing said visualsignal while the fabric is operated by said feeding means and saidcircuit-closing element maintained out of contact, means for energizingsaid audible signal when said circuit-closing element closes saidelectric circuit through a hole in the moving fabric and a condenserconnected in shunt with 1 1 said input circuit, said condenser having acapacity sufficient to receive a charge from said potential source andto maintain said charge for prolonging the time interval over which saidinput circuit is controlled for correspondingly controlling the timeinterval during which said audible signal is operated.

16. An apparatus for detecting holes in tubular fabric as set forth inclaim 15 in which said condenser is elec trically connected in saidinput circuit in a position intermediate said control grid and saidsource of potential for receiving an electric charge simultaneously withthe closing of said circuit-closing element, and means for utilizing thecharge in said condenser for determining the potential on said grid andmaintaining said relay in a position for operating said audible signalfor a predetermined time period subsequent to the opening of saidcircuit-closing element.

17. An apparatus for detecting holes in tubular fabric as set forth inclaim 15 in which said condenser is electrically charged from saidsource prior to the completion of the electrical connection of saidaudible signal with said contactors.

18. Apparatus for detecting holes in tubular fabric comprising aspreader around and over which the fabric passes, a feeler supportedoutwardly of said spreader and having a portion biased against thefabric passing thereover to be movable through a hole in the fabric, anddetecting means responsive to such movement of said feeler portionthrough the fabric.

19. In an apparatus for detecting holes in fabric and capable ofdetecting holes in tubular fabric, feeding means for feeding the fabricin spread condition, an electric detecting circuit capable of detectingholes in the fabric while the fabric is moving, said detecting circuitclosing an electric circuit, an electron tube system having,

input and output circuits, a potential source, a condenser connected insaid input circuit, a circuit extending from one side of said condenserthrough said circuit-closing element and returning through saidpotential source to the other side of said condenser, said condenserhaving a capacity sufficient to receive a charge from said potentialsource while said circuit-closing element is closed and maintain saidcharge after said circuit-closing element is open for prolonging theeffect of said circuit-closing operation upon said electron tube systembeyond the time interval that said circuit-closing element remainsclosed, and an alarm connected with said output circuit and operativeover the time period that said effect of said circuit-closing operationis prolonged powered from the discharge of said condenser through theinput circuit of said electron tube system.

References Cited in the file of this patent UNITED STATES PATENTS701,248 Bannon May 27, 1902 1,149,018 Beregh Aug. 3, 1915 1,631,476 MoosJune 7, 1927 1,980,294 Ross et al Nov. 13, 1934 2,105,185 Degnan Ian.11, 1938 2,304,513 Stearns Dec. 8, 1942 2,611,017 Bailey Sept. 16, 1952

1. APPARATUS FOR DETECTING HOLES IN TUBULAR FABRIC, COMPRISING ASPREADER OF CONDUCTING MATERIAL AROUND AND OVER WHICH THE FABRIC PASSESIN ONE DIRECTION LENGTHWISE OF THE FABRIC, A FEELER ENGAGEABLE WITH THEFABRIC OUTWARDLY OF SAID SPREADER AND MOVABLE INTO ELECTRICAL CONTACTTHEREWITH UPON THE PASSING OF A HOLE IN THE FABRIC UNDER SAID FEEDER,AND A DETECTING CIRCUIT INCLUDING SAID FEELER AND SAID SPREADER, SAIDCIRCUIT FURTHER COMPRISING A PAIR OF CONTACT DEVICES, ONE CARRIED BY ANDELECTRICALLY CONNECTED TO SAID SPREADER, AND THE OTHER ARRANGEDEXTERNALLY OF THE FABRIC AND IN ELECTRICAL ENGAGEMENT WITH SAID ONECONTACT DEVICE THROUGHOUT MOVEMENT OF THE FABRIC OVER SAID SPREADER.